The need for better materials to effectively fill voids left by burning or melting cable insulation in the case of a fire in modern buildings or in power stations has long been recognized. Better thermal insulating coverings for walls, doors, ceilings, etc. are also needed. Such materials have the property of remaining in an unexpanded flexible form until heat, such as that produced by a fire, is applied, at which time they will expand to become substantially rigid refractory thermal insulators.
The materials and processes heretofore employed, as described below, have certain disadvantages. They usually provided protection for only limited periods of time because of poor stability at elevated temperatures or damage by high-pressure water sprays due to low mechanical strength. They have had the further disadvantage that they were not water-proof and had low volume expansions and pressure generation, particularly at low temperatures, with a resultant loss in their capacity to fill void areas or provide thermal insulation, thus allowing the spread of smoke or fire.
U.S. Pat. No. 3,786,604 is illustrative of the prior art and discloses the concept of filling the gap between a concrete floor slab and an upright curtain wall with a urea formaldehyde resin foam which is supported in a though made of thin resilient sheet steel. The steel though support is required because of mechanical strength of the foam is relatively low and that of the charred foam is even lower.
U.S. Pat. No. 3,429,836 discloses a process for producing thermal insulating coverings from organic (poly-styrene and copolymers of styrene) foam materials in combination with alkali metal silicates. The composition is made into rigid boards for use as thermal insulating covers on surfaces such as walls, ceilings, doors, and the like. The formed board-like material must be coated with a protective layer of lacquers or plastic films to render it moisture resistant.
U.S. Pat. No. 3,983,082 relates to a silicone resin base fire retardant system having a temperature capability to at least about 230.degree. C. and combines intumescent characteristics with a crusting and charring capability. These materials are intended primarily for use in aircraft gas turbine engines and they are most effective at relatively high temperatures on the order of 1000.degree. C. or higher.
U.S. Pat. No. 4,273,879 relates to a product which contains only solid materials, its matrix being principally vulcanized rubber. The product can only be manufactured by the use of dry rubber techniques and the flexible rubber like material thus prepared then has to be shaped and die cut to form products of desired sizes and shapes. Thus additional steps in the manufacturing are required.
It is accordingly an object of this invention to provide a one-step process for the manufacture of intumescent fire retardant materials of desired sizes and shapes.
It is another object of this invention to provide a composition for use in this process.
Other objects will appear from the description which follows.